Israel says Prime Minister Benjamin Netanyahu sought to meet with President Obama at the U.N. but was turned down. The issue threatens to spill into the campaign.

WASHINGTON — The White House struggled Tuesday to dispel reports that it had snubbed a request for a meeting this month from Israeli Prime Minister Benjamin Netanyahu, as friction between the two allies again burst into the open.

As Netanyahu stepped up his criticism of President Obama's approach to the Iran nuclear threat, Israeli officials disclosed that Netanyahu had sought unsuccessfully to schedule a meeting with Obama at the upcoming United Nations General Assembly session in New York. Netanyahu's office had been told, Israeli officials said, that Obama would not be at the U.N. on Sept. 27 and 28, when Netanyahu would be there.

After a day of news reports about the escalating feud, the White House arranged an evening phone call between Obama and Netanyahu and insisted in a statement that the leaders had discussed "our close cooperation on Iran and other security issues." It denied that the Israelis had asked for a meeting in Washington and added, "nor was a request for a meeting ever denied."

But the Israeli government, in a statement Tuesday night, confirmed that Netanyahu had sought a meeting in New York on the sidelines of the U.N. session, a time when national leaders often confer.

The back and forth came only hours after Netanyahu, in comments in Israel, had unleashed his most scalding criticism of the Obama administration's approach to Iran's nuclear program.

Netanyahu condemned the administration for refusing to issue a more specific ultimatum to Iran over the nuclear program, saying that those who refuse to make such demands of Tehran "don't have a moral right to place a red light before Israel." He was referring to the continuing U.S. pressure on Israel not to bomb Iran to try to halt its nuclear program.

The intensifying criticism marks a sharp departure from usual practice in U.S.-Israeli relations, where disagreements are supposed to remain private. And it is also threatening to spill over into the political campaign. Republicans seized on the reported snub as more evidence that Obama has not been a steadfast friend of Israel.

Netanyahu's comments marked the second day this week that he had publicly criticized the administration. White House officials pushed back, saying on Monday that making more explicit threats would only work against international efforts to pressure Iran through economic sanctions to curb its nuclear program.

"Both the U.S. and Israel are seeing an escalatory pattern to statements from the other, and interpreting the worst to the other side's political intentions, even if there is a case to be made that both sides actually have a preference to be on the same page," said David Makovsky, a Mideast analyst at the Washington Institute for Near East Policy. "This is tragic and the only winner is Iran."

The Obama administration has worked hard to counter criticism from conservatives that it has been an unreliable ally to Israel, a critique the Romney campaign hopes will make inroads with Jewish voters, a largely loyal Democratic constituency. The shift of even a small fraction of those voters in Florida could make a difference.

The administration's apparent willingness to challenge Netanyahu this week stirred speculation that Obama may now see some political advantage in resisting pressure that could lead to another war.

With Americans weary from two wars, "there's a case to be made that on the political level, the American public, and even American Jews, are on Obama's side on this one," said one Mideast analyst, who declined to be identified because of the sensitivity of the issue.

He speculated that Obama might also have decided against going out of his way to arrange a meeting with Netanyahu in New York because of his frustration with criticism that has gone on for months.

"I wouldn't be surprised if the president has gotten a little bit frustrated and decided, 'I'm not rewarding this behavior,'" the analyst said.

A statement from Sen. Kelly Ayotte (R-N.H.) suggested that the dispute might soon become visible in the campaign.

"It's troubling that the president couldn't find time in his schedule to meet with the leader of our closest and most reliable ally in the Middle East," she said. "It appears that this administration is more focused on preventing Israel from protecting its own sovereignty than preventing Iran from achieving nuclear weapons capability."